diff --git a/src/calibre/library/server/base.py b/src/calibre/library/server/base.py
index 26e4d3469e..d18bffc6a2 100644
--- a/src/calibre/library/server/base.py
+++ b/src/calibre/library/server/base.py
@@ -34,7 +34,7 @@ class DispatchController(object): # {{{
     def __init__(self, prefix, wsgi=False):
         self.dispatcher = cherrypy.dispatch.RoutesDispatcher()
         self.funcs = []
-        self.seen = set([])
+        self.seen = set()
         self.prefix = prefix if prefix else ''
         if wsgi:
             self.prefix = ''